If you want to produce your eBook quickly and easily produce it as a PDF. If you need to produce it as an ePub (fixed or variable) and as a mobi (for Kindle), you will need to repurpose your original inDesign file and learn how to do so, which will take some time.
There are a number of excellent tutorials on Lynda.com and books, such as those by Liz Castro, and, of course, help on the InDesign ePub forum with individual issues.